Tracking 3D seismic horizons with a new hybrid tracking algorithm

We have developed a new algorithm for tracking 3D seismic horizons. The algorithm combines an inversion-based, seismic-dip flattening technique with conventional, similarity-based autotracking. The inversion part of the algorithm aims to minimize the error between horizon dips and computed seismic dips. After each cycle in the inversion loop, more seeds are added to the horizon by the similarity-based autotracker. In the example data set, the algorithm is first used to quickly track a set of framework horizons, each guided by a small set of user-picked seed positions. Next, the intervals bounded by the framework horizons are infilled to generate a dense set of horizons, also known as HorizonCube. This is done under the supervision of a human interpreter in a similar manner. The results show that the algorithm behaves better than unconstrained flattening techniques in intervals with trackable events. Inversion-based algorithms generate continuous horizons with no holes to be filled posttracking with a gridding algorithm and no loop skips (jumping to the wrong event) that need to be edited as is standard practice with autotrackers. Because editing is a time-consuming process, creating horizons with inversion-based algorithms tends to be faster than conventional autotracking. Horizons created with the adopted algorithm follow seismic events more closely than horizons generated with the inversion-only algorithm, and the fault crossings are sharper.

Genetic reproductive risk in pericentric inversion carriers

Перицентрические инверсии (ПИ) - это сбалансированные структурные хромосомные перестройки, частота которых в популяции варьирует от 0,12% до 0,7% [1]. Особенностью синапсиса и рекомбинации ПИ в мейозе является формирование инверсионной петли, единичный кроссинговер в которой может приводить к образованию рекомбинантных хромосом c дупликацией/делецией дистального по отношению к инверсии сегмента короткого плеча и делецией/дупликацией дистального сегмента длинного плеча соответственно. Клиническая значимость ПИ определяется риском формирования у носителя гамет (зигот) с хромосомным дисбалансом (ХД), приводящим к раннему спонтанному прерыванию беременности, мертворождению или рождению детей с пороками и/или аномалиями развития. Проведена оценка эмпирической частоты формирования сперматозоидов с рекомбинантными хромосомами, а также риска формирования гамет и выживаемости потенциальных зигот с ХД у четырех мужчин-носителей ПИ. Pericentric inversion are intrachromosomal balanced structural abnormalities. The frequency in the general population is ranged from about 0.12% to 0.7% [1]. To provide complete synapsis and recombination during meiosis pairing of the normal and inverted chromosomes requires the formation of inversion loop. One crossover within the inversion loop leads to the production of two complementary recombinant chromosomes with both duplicated and deleted chromosome segments including the regions distal to the inversion. The particular clinical relevance of inversion chromosomes is that they can set the stage for the generation of recombinant gametes that may lead to early miscarriages, stillbirth or congenital abnormalities. The estimation of empiric frequencies of recombinant spermatozoa, risk of abnormal gamete formation and potential zygote viability in four pericentric inversion carriers was performed.

A Study on Dynamic Inversion of UAV

In this paper, preliminary effort of pre-flight test lateral control method study is presented. Parameters and coefficients of candidate UAV (Unmanned Aviation Vehicle) are calculated for modeling and linearization. For controller design, dynamic inversion is used to cancel the dynamic coupling between attitudes. Stability of inversion loop controller which applied on non-ideal inversion is studied. Finally, simulation is present to compare the PI and nonlinear PI controller based on dynamic inversion.

Synapsis and recombination in inversion heterozygotes

Inversion heterozygotes are expected to suffer from reduced fertility and a high incidence of chromosomally unbalanced gametes due to recombination within the inverted region. Non-homologous synapsis of the inverted regions can prevent recombination there and diminish the deleterious effects of inversion heterozygosity. The choice between non-homologous and homologous synapsis depends on the size of inversion, its genetic content, its location in relation to the centromere and telomere, and genetic background. In addition, there is a class of inversions in which homologous synapsis is gradually replaced by non-homologous synapsis during meiotic progression. This process is called synaptic adjustment. The degree of synaptic adjustment depends critically on the presence and location of the COs (crossovers) within the inversion loop. Only bivalents without COs within the loop and those with COs in the middle of the inversion can be completely adjusted and became linear.

Synaptonemal complex spreading in Allium ursinum: pericentric asynapsis and axial thickenings

In Allium ursinum meiotic pairing of homologues is always incomplete; a proximal region on each bivalent remains regularly unsynapsed even in late pachytene. The spatial correlation of the unsynapsed region with the kinetochore suggests that the kinetochore itself exerts an inhibitory effect on synapsis in its vicinity. This can be interpreted as the cytological basis of the ‘centromere effect’ on recombination in this species. Moreover, the high incidence of a pericentric inversion loop in a heterozygous chromosome pair shows that proximal pairing initiation is possible and that its failure cannot be responsible for pericentric asynapsis. The formation of the inversion loop is complicated by the need for two independent pairing initiation sites because synapsis cannot proceed across the pericentric region. It is proposed that the meiotic bouquet polarization helps in establishing the presynaptic alignment of the homologous sites within the inverted regions and hence to achieve a high rate of inversion loop formation. Thickenings of the axial/lateral elements are not distributed equally along the synaptonemal complex. They are underrepresented in unpaired axes but strikingly abundant at the borders with synapsed regions, suggesting their origin in the pairing forks during the process of synapsis. They are virtually always present at nucleolus-organizing regions and often they appear at corresponding sites on opposite lateral elements. Besides the thickenings several other kinds of axial deformities are present in unpaired axes.

AN INTERSTITIAL PERICENTRIC INVERSION IN NEUROSPORA

In ln(IL; IR)OY323 of Neurospora crassa, a long central segment of linkage group I is inverted that includes the centromere. This is the first interstitial pericentric inversion to be identified in a fungus. In genetic and cytological behavior, it resembles chromosome inversions in higher eukaryotes. In crosses heterozygous for the OY323 inversion, normally distant markers are closely linked, while in homozygous inversion crosses the gene order is reversed, but recombination is approximately normal within the inverted segment. A characteristic inversion loop may form at pachytene in heterozygous crosses; frequently, segments distal to the breakpoints do not pair, however. Rearrangement breakpoints were mapped precisely by duplication coverage using appropriate recessive markers in crosses of OY323 with a partially overlapping inversion, In(IL→IR)NM176.

TECHNIQUES FOR MANIPULATING CHROMOSOMAL REARRANGEMENTS AND THEIR APPLICATION TO DROSOPHILA MELANOGASTER. I. PERICENTRIC INVERSIONS

ABSTRACT Techniques have been developed for manipulating pericentric inversions in Drosophila that are based on the lethality of grossly aneuploid zygotes and the existence of recombinationally interconvertible genotypes for any heterozygous inversion complex: males of some of these genotypes will produce only aneuploid sperm, which can be used to rescue complementary aneuploid ova and selectively recover recombinational derivatives of inversions. Markers can be recombined into inversions through a sequence of selected single exchanges, and a novel type of duplication can be synthesized from overlapping inversions that has the characteristics of both insertional and tandem duplications; there are also applications to half-tetrad analyses.——Two cytogenetic screens are developed: (1) the dominant lethality of a large insertional-tandem duplication can be reverted by deletional events that give rise to net deficiencies or duplications, and (2) deficiencies and tandem duplications in proximal regions can be selectively recovered as the results of unequal exchanges within an inversion loop. Recombinants have been recovered between breakpoints separated by distances of as little as fifty bands, arguing against the existence of some small number of sites necessary for the initiation of recombinational pairing. In several instances, hyperploids for four to six numbered divisions were observed to be fertile in both sexes.